It is known that use of molded resin products as interior and/or exterior parts of automobiles is advantageous for reducing weight of automobiles. A well-known resinous material employed for producing the molded resin product is a propylene polymer composite comprising a propylene polymer as a main component and auxiliary components such as an inorganic filler and an elastomer. The propylene polymer is thermoplastic resin which is good in molding characteristics and thermal stability. The inorganic filler and elastomer are employed to improve flexural properties and impact resistance of the molded product.
Examples of the inorganic filler include a fibrous inorganic filler and a non-fibrous inorganic filler. Examples of the fibrous inorganic filler include fibrous basic magnesium sulfate and fibrous potassium titanate. Examples of the non-fibrous inorganic filler include talc and mica.
U.S. Pat. No. 7,655,721 B2 (corresponding to JP 2006-83369 A) discloses a method for preparing a propylene-based resin composition containing a fibrous inorganic filler, a non-fibrous inorganic filler and an elastomer. The disclosed method employs a master batch resin composition (preferably, in the form of pellets) comprising a first propylene polymer and a fibrous inorganic, filler. The master batch composition is then mixed with a second propylene polymer, a non-fibrous inorganic filler and an elastomer to give the target resin composition. U.S. Pat. No. 7,655,721 B2 further describes that the molded resin product produced using the fibrous inorganic filler-containing propylene-based master batch pellets is superior in balance between rigidity and impact resistance.
Recently, the requirement for further reducing weights of the interior and/or exterior parts of automobiles has increased. This means that a molded resin product produced from a resin composition should have increased physical strength such as increased flexural strength and increased impact resistance.